Device and method for controlling transfer voltage in an electrophotographic recording apparatus

Abstract

A device and method for controlling a transfer voltage in an electrophotographic recording apparatus for printing by the page. In the transfer voltage controlling device, a high voltage generator generates a transfer voltage, an exposer starts and stops an exposure in response to a first exposure signal and a second exposure signal, respectively, a transfer roller transfers an image by high pressure with the transfer voltage received from the high voltage generator, and an engine controller generates the first exposure signal for starting an exposure for one page and the second exposure signal for terminating the exposure for the page, and causes the high voltage generator to supply or stop the transfer voltage to the transfer roller upon generation of the first exposure signal or the second exposure signal, respectively.

What is claimed is: 
     
       1. A transfer voltage controlling device in an electrophotographic recording apparatus, comprising: a high voltage generator for generating a transfer voltage;   an organic photoconductive drum on which an image is formed for printing;   an exposer for exposing a surface of the organic photoconductive drum to form an image on the surface of the organic photoconductive drum in response to a first exposure signal for starting an exposure to form the image and in response to a second exposure signal for stopping the exposure to form the image;   a transfer roller for transferring the image formed on the surface of the organic photoconductive drum by pressure with the transfer voltage supplied from the high voltage generator; and   an engine controller for generating the first exposure signal for starting an exposure to form the image for a page on which the image is to be printed and for generating the second exposure signal for terminating the exposure to form the image for the page on which the image is to be printed, and for causing the high voltage generator to selectively supply the transfer voltage to the transfer roller dependent upon generation of the first exposure signal and to selectively stop the supply of the transfer voltage to the transfer roller dependent upon generation of the second exposure signal.   
     
     
       2. The transfer voltage controlling device of claim 1, further comprising a memory for storing a first time required for an exposed portion of the organic photoconductive drum to reach the transfer roller and for storing a second time required for the transfer voltage supplied to the transfer roller to reach a stable level, and wherein the engine controller is also for generating a first control signal to cause the high voltage generator to start the supply of the transfer voltage to the transfer roller at a time point determined by a sum of the first time and a time when the first exposure signal is output from the engine controller to the exposer and then subtracting the second time from the sum. 
     
     
       3. The transfer voltage controlling device of claim 2, wherein the memory is also for storing a third time required for completely transferring a toner image with the transfer voltage supplied to the transfer roller and for storing a fourth time required for a last exposed portion of the organic photoconductive drum to reach the transfer roller, and wherein the engine controller is also for generating a second control signal to cause the high voltage generator to stop the supply of the transfer voltage to the transfer roller at a time point determined by a sum of the third time, the fourth time and a time when the second exposure signal is output from the engine controller to the exposer. 
     
     
       4. The transfer voltage controlling device of claim 1, further comprising a memory for storing a toner image transfer time required for completely transferring a toner image with the transfer voltage supplied to the transfer roller and for storing a last exposed portion time required for a last exposed portion of the organic photoconductive drum to reach the transfer roller, and wherein the engine controller is also for generating a control signal to cause the high voltage generator to stop the supply of the transfer voltage to the transfer roller at a time point determined by a sum of the toner image transfer time, the last exposed portion time and a time when the second exposure signal is output from the engine controller to the exposer. 
     
     
       5. A transfer voltage controlling method in an electrophotographic recording apparatus for printing on a page, comprising the steps of: sensing a time when a first exposure signal for initially driving an exposer is generated;   starting to supply a transfer voltage to a transfer roller dependent upon generation of the first exposure signal;   sensing a time when a second exposure signal for terminating the operation of the exposer for the last time is generated; and   stopping the supply of the transfer voltage to the transfer roller dependent upon generation of the second exposure signal.   
     
     
       6. The transfer voltage controlling method of claim 5, further comprising the steps of: continuously supplying the transfer voltage to the transfer roller if an exposure signal is absent for a time period shorter than a predetermined time period; and   stopping the supply of the transfer voltage to the transfer roller if an exposure signal is absent for a time period at least equal to the predetermined time period.   
     
     
       7. The transfer voltage controlling method of claim 6, further comprising the step of resuming the supply of the transfer voltage to the transfer roller upon output of an exposure signal after stopping the supply of the transfer voltage to the transfer roller. 
     
     
       8. A transfer voltage controlling method in an electrophotographic recording apparatus for printing on a page, comprising the steps of: generating a first exposure signal for starting an exposure for forming an image;   supplying a transfer voltage to a transfer roller for transferring the image in response to generation of the first exposure signal;   generating a second exposure signal for terminating the exposure for forming the image; and   stopping the supplying of the transfer voltage to the transfer roller in response to generation of the second exposure signal.   
     
     
       9. The transfer voltage controlling method of claim 8, further comprising the steps of: generating a first control signal for starting the supplying of the transfer voltage to the transfer roller at a time point determined by a sum of a time required for an exposed portion of an organic photoconductive drum to reach the transfer roller and a time when the first exposure signal is generated and then subtracting from the sum a time required for the transfer voltage supplied to the transfer roller to reach a stable level; and   generating a second control signal for stopping the supplying of the transfer voltage to the transfer roller at a time point determined by a sum of a time required for a last exposed portion of the organic photoconductive drum to reach the transfer roller, a time required for completely transferring a toner image with the transfer voltage supplied to the transfer roller and a time when the second exposure signal is generated.   
     
     
       10. The transfer voltage controlling method of claim 8, further comprising the steps of: continuously supplying the transfer voltage to the transfer roller if an exposure signal is absent for a time period shorter than a predetermined time period; and   stopping the supplying of the transfer voltage to the transfer roller if an exposure signal is absent for a time period at least equal to the predetermined time period.   
     
     
       11. The transfer voltage controlling method of claim 10, further comprising the step of resuming the supplying of the transfer voltage to the transfer roller upon generation of an exposure signal after stopping the supplying of the transfer voltage to the transfer roller. 
     
     
       12. A transfer voltage controlling apparatus for electrophotographic printing, comprising: a high voltage generator for generating a transfer voltage;   an exposer for starting and stopping an exposure in response to a first exposure signal and a second exposure signal, respectively;   a transfer roller for transferring an image by high pressure with the transfer voltage supplied from the high voltage generator; and   an engine controller for generating the first exposure signal for starting an exposure for a page to be printed and for generating the second exposure signal for terminating the exposure for the page to be printed, and for causing the high voltage generator to selectively supply and stop the transfer voltage to the transfer roller in response to generation of the first exposure signal and the second exposure signal, respectively.